Method for operating an active thermal energy storage system

ABSTRACT

An active thermal energy storage system is disclosed which uses an energy storage material that is stable at atmospheric pressure and temperature and has a melting point higher than 32 degrees F. This energy storage material is held within a storage tank and used as an energy storage source, from which a heat transfer system (e.g., a heat pump) can draw to provide heating of residential or commercial buildings and associated hot water. The energy storage material may also accept waste heat from a conventional air conditioning loop, and may store such heat until needed. The system may be supplemented by a solar panel system that can be used to collect energy during daylight hours, storing the collected energy in the energy storage material. The stored energy may then be used during the evening hours to heat recirculation air for a building in which the system is installed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. non-provisionalpatent application Ser. No. 11/818,401, filed Jun. 13, 2007, whichclaims priority from U.S. provisional patent application Ser. No.60/852,844, filed Oct. 19, 2006, the entirety of which applications areincorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a system for heating and cooling of residentialand commercial building spaces and hot water systems, and moreparticularly to an active heat transfer system used for use inefficiently controlling air and water temperature in commercialbuildings and residences.

BACKGROUND OF THE INVENTION

The electrical energy generation and distribution networks in the UnitedStates are currently stressed to the limit by peak demands duringdaytime hours. Quite expectedly, the demands of the industrial sector,commercial and residential air conditioning and water heating arehighest during the daytime hours. During the off peak, late evening andnight time hours, the opposite is true, and there normally is excesselectrical power available which is not needed in the local power grid.

Using nationwide transmission power lines, the power generation anddistribution grid is used to transfer excess power to other grids thatrequire it. This is a form of load leveling that is aimed at maintainingthe coal, oil or nuclear power generation plants at a level, constant,load. The problem with such a load leveling scheme is that costs arehigh, due to the costs of transmission and line losses inherent incross-country transmission to other power grids.

Further, coal fired electric generating plants in the United States emitcarbon dioxide and other pollutants to the atmosphere in proportion topeak electric daytime demands. The peak daytime demands determine theamount of excess off peak evening power that must be transported (again,by costly high voltage power transmission lines), to a far away electricgrid that can use the power for their peak power shortage needs, orother use.

It would be advantageous to provide a system that enables local off-peakutilization of the excess power from the local grid, thus reducing costsassociated with peak production, pollution associated with that peakproduction, and also reducing costs associated with transmission ofexcess power over long distances.

SUMMARY OF THE INVENTION

A system is disclosed for storing excess local grid power producedduring off peak hours (e.g., night, holidays, etc.), for use incontrolling heating/cooling systems in residential and commercialbuildings during peak (e.g., daytime) periods. An active thermal energystorage system (hereinafter referred to as “ATESS”) is disclosed forstoring this excess local grid off peak power in a thermal energystorage material, such as that described in U.S. Pat. No. 3,976,584 toLeifer, and for using the stored energy to control air and watertemperatures in residential dwelling and/or commercial buildings duringpeak energy periods. It will be appreciated, however, that the ATESS maybe used to provide energy for heating/cooling at any time during a 24hour day, and not just during the peak energy periods.

The ATESS may enable local use of off peak excess electrical energy,thus reducing the need for oil and natural gas systems previouslyrequired for residential dwelling or commercial building heating and/orwater heating needs. Thus, the invention relates to the active transferof thermal heat energy obtained from any of a variety of natural energysources (e.g., solar, electrical, wind, gas, oil, etc.) by an activemethod and then storing that thermal heat energy in a thermal energystorage material, such as one of the materials described in U.S. Pat.No. 3,976,584 to Leifer, the entire contents of which patent isincorporated herein. The thermal energy storage material may becontained in an appropriate tank or storage vessel (which will bedescribed in greater detail below), and the thermal energy stored in thethermal energy storage material may then be transferred by an activeheat transfer system (e.g., a heat pump) to a point of use locationwithin a residential home or commercial building, when needed for airand/or water heating at any time during a 24 hour day.

The ATESS operates on the principal of collecting limited availableinput energy from any and all sources (e.g., solar, electricity, wind,oil, gas) and storing that energy in a thermal energy storage materialuntil needed later. The energy stored in the thermal energy storagematerial may be removed by a heat transfer system (e.g., heat pump) tocontrol the temperature of residential homes or commercial buildings,thus providing the heat energy requirements at any time during a 24 hourday. Hot water or other liquid heating needs can be met by use of a dualintegrated or separate heat transfer (e.g., heat pump) system which cantransfer the stored energy from the energy storage material as neededfor such purpose.

In one example, systems exist for collecting solar energy from the sun'sradiation only during the limited day time hours for use in home air orwater heating needs. However, such systems can only provide this energywhen the sun is available. During the evening hours or on cloudy daysthe residential dwelling and/or commercial building air and/or waterheating energy needs must be obtained from or supplemented by otheravailable sources of energy, such as oil, natural gas, wind orelectrical energy. Thus, alternative sources of energy are required inorder to satisfy the full 24 hours of energy needs. The ATESS functionsto receive solar energy during daylight hours, and to store that energyin a thermal energy storage material for use at any time during a 24hour period. Stored energy is then transferred to the area of need by anactive heat transfer (e.g., heat pump) system. In this way, the ATESScan make solar energy available 24 hours a day, thus reducing the needfor oil or natural gas for residential dwelling and/or commercialbuilding heating and/or water heating energy needs.

In another example, during hot and humid summer months the ATESS can beused to remove heat energy from the air within a residential orcommercial building, store that heat energy in the thermal energystorage material, and then make that heat energy available for use atany time during the day or night.

Currently residential dwellings and/or commercial buildings use airconditioning powered by electricity to remove heat from the air insidethe dwellings and/or buildings. Electrical energy is required to removethe heat energy from the inside building room air to make it comfortablefor human occupancy during hot humid days and nights. The ATESS can beconfigured so that the active heat transfer system (e.g., heat pump)removes heat from the air inside a building, and stores it in thethermal energy storage material. This stored waste heat, which isnormally rejected to the outside atmosphere by typical air conditioningunits, can then be used to heat the water used in the residentialdwellings and/or commercial buildings. It can also be used to providenight time heating needs, as appropriate.

The ATESS will reduce markedly the daytime peak power electric demandson the electrical power grid and the electric generating equipment ofthe local power companies. The ATESS enables more efficient local use ofenergy from the local power grid, thus reducing or eliminating the needfor oil and natural gas. Concurrent reductions in the emission of carbondioxide and other pollutants, normally associated with energy productionfrom oil or natural gas, would also be achieved.

An thermal energy storage system is disclosed, comprising a first tankfor holding a quantity of water, a second tank having a quantity ofthermal energy storage material disposed therein, the thermal energystorage material comprising a substantially solid clathrate having amelting point above 32 degrees Fahrenheit (F.), and a latent heat offusion approaching that of water, and recirculation piping connectingthe first and second tanks. The recirculation piping may be in fluidcommunication with an inner volume of said first tank, the recirculationpiping further comprising a heating coil disposed within the secondtank. Thusly arranged, heated water disposed in said first tank at afirst time may be movable within said recirculation piping, and throughsaid heating coil, to transfer heat from the heated water to the thermalenergy storage material disposed within the second tank. Furthermore,cool water disposed in said first tank at a second time is movablewithin said recirculation piping, and through said heating coil, totransfer heat from said thermal energy storage material disposed withinthe second tank to the cool water.

A thermal energy storage system is disclosed, comprising a hot watertank for holding a quantity of water, a storage tank having a quantityof thermal energy storage material disposed therein, the thermal energystorage material comprising a substantially solid clathrate having amelting point above 32 degrees Fahrenheit (F.), and a piping loopconnecting the hot water tank and the storage tank. The piping loop maybe in fluid communication with an inner volume of said hot water tank,the piping loop further comprising a heating coil disposed within thestorage tank. When a quantity of water in said hot water tank has atemperature greater than a temperature of said thermal energy storagematerial, said water is movable within said piping loop and heating coilto transfer heat from the water to the thermal energy storage material.When said quantity of water in said hot water tank has a temperatureless than a temperature of said thermal energy storage material, saidwater is movable within said piping loop and heating coil to transferheat from the thermal energy storage material to the water.

A thermal energy storage system, comprising a first tank, a second tank,and an air distribution system. The first tank may have a quantity ofwater disposed therein. The second tank may have a quantity of thermalenergy storage material disposed therein. The thermal energy storagematerial may comprise a phase change material having a melting pointabove 32 degrees Fahrenheit (F.), and a latent heat of fusionapproaching that of water. The first and second tanks may be connectedby a recirculation loop for moving said water from said first tankthrough a first coil disposed within said second tank to transfer energybetween said water and said thermal energy storage material. Said secondtank and said air distribution system may be connected by an airconditioning loop for moving a first heat transfer fluid from a secondcoil disposed in said second tank to a third coil disposed in said airconditioning system to transfer energy between said thermal energystorage material and air passed over said third coil.

A thermal energy storage system is disclosed, comprising a first tank, asecond tank, and a hot water radiator circulation system. The first tankmay have a quantity of water disposed therein. The second tank may havea quantity of thermal energy storage material disposed therein, thethermal energy storage material comprising a phase change materialhaving a melting point above 32 degrees Fahrenheit (F.), and a latentheat of fusion approaching that of water. The first and second tanks maybe connected by a recirculation loop for moving said water from saidfirst tank through a first coil disposed within said second tank totransfer energy between said water and said thermal energy storagematerial. The second tank and the hot water radiator circulation systemmay be connected by loop for moving a first heat transfer fluid from asecond coil disposed in said second tank to a water coil disposed insaid hot water radiator circulation system to transfer energy betweensaid thermal energy storage material and water passed over said watercoil.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the ATESS installed in a dwelling that has an oil ornatural gas hot air furnace system;

FIG. 2 shows the ATESS installed in a dwelling having an oil or naturalgas hot air furnace system supplemented with solar water heatingcollector panels;

FIG. 3 shows the ATESS installed in a dwelling having an oil or naturalgas hot air furnace system and has a separate water heating system (heatpump);

FIG. 4 shows the ATESS installed in a dwelling having an oil or naturalgas hot air furnace system and has a separate water heating system (heatpump), and which further comprises a dual control system for use as anair conditioner;

FIG. 5 shows the ATESS described in FIG. 3 with photovoltaic solarcollection panels for cold winter weather operation; and

FIG. 6 shows the ATESS described in FIG. 4 with photovoltaic solarcollection panels for hot summer weather operation;

FIG. 7 is a schematic an arrangement of an ATESS test facility used totest system and thermal energy storage material efficacy;

FIG. 8 is a tabular representation of the results of a 14 day test ofthe ATESS;

FIG. 9 is a tabular representation of the performance of the ATESS on anhourly basis throughout a 24-hour day; and

FIGS. 10A-C are tabular representations of daily fuel oil and LPG(liquid propane gas) consumption for a residential home, including acomparison of the annual winter heating costs for fuel oil, LPG, and theATESS heating system using off peak electric and daytime solar, all offpeak electricity, and all daytime solar.

DETAILED DESCRIPTION

As previously noted, there are many sources of energy (e.g., solar,electrical, oil, gas, wind, etc.) which may be available for collectiononly during limited time periods during a 24 hour day. This is incontrast to the electrical, heating or cooling power needs associatedwith a residential or commercial building, which may vary during anygiven 24 hour period. The disclosed ATESS accommodates such limitedavailability of these energy sources and provides a steady source ofenergy, as needed, throughout a 24 hour period.

Referring to FIG. 1, the ATESS 1 is shown installed in the basement area2 of a dwelling having an oil or natural gas hot air furnace system 4.The ATESS 1 may comprise a storage tank 6 containing a quantity ofthermal energy storage material 8, a hot water storage tank 10 forheating and distribution of hot water through the residence, and aconnection 12 between the storage tank 6 and the furnace system 4 toallow the transfer of heat between the thermal energy storage material 8and the furnace system 4. A connection 14 will also be provided betweenthe hot water tank 10 and the storage tank 6 to allow the transfer ofheat between the thermal energy storage material 8 contained in thestorage tank 6 and the hot water from the hot water tank 10.

The connection 12 between the storage tank 6 and the furnace system 4may comprise fluid supply and return piping 16, 18 which connect toopposite ends of a condenser coil 20 located within the furnace system4. Likewise, the supply and return piping 16, 18 connect to oppositeends of an evaporator coil 22 located within the storage tank 6. Thesupply and return piping 16, 18 and condenser and evaporator coils 20,22 thus form a closed loop for the movement of a heat transfer fluidbetween the furnace system 4 and the thermal energy storage materialtank 6. The flow rate of the heat transfer fluid may be controlled byoperation of a compressor 24 located in the return piping 18, and acontrol valve 26 located in the supply piping 16.

Likewise, the connection 14 between the thermal energy storage materialtank 6 and the hot water tank 10 may comprise supply 28 and return 30piping connected to a heating coil 32 disposed within the storage tank6. Water is pumped through the supply and return piping 28, 30 by acirculation pump 34 located in the supply piping line. A check valve 36disposed within the discharge piping protects against backflow of waterthrough the return piping when the pump 34 is turned off. The hot watertank 10 may farther have a cold water supply line 38 for providing aconstant source of water to the tank 10 for heating, and a hot waterdischarge line 40 for distributing the heated water throughout theresidence.

The hot water tank 10 may further have one or more electrical resistanceheaters 52, 54 to heat the water in the tank to a desired temperatureusing building electricity.

In operation, the water in the hot water tank 10 is heated to a desiredtemperature using one or more of the resistance heaters 52, 54. Theheated water may then be pumped through the supply and return piping 28,30 to heat the thermal energy storage material 8 contained in thethermal energy storage material tank 6. This heat transfer can occuruntil a desired amount of energy is contained in the thermal energystorage material 8.

Thereafter, the energy contained in the thermal energy storage material8 can be transferred to the air 46 of the furnace system 4 via the fluidsupply and return lines 16, 18. The heat transfer fluid contained inthese lines may be warmed as it passes through the evaporator coil 22and compressor 24. Energy contained in the heat transfer fluid is thentransferred to the recirculating air 46 via the condenser coil 20,providing warm air 50 to be returned to the living space.

The energy in the thermal energy storage material 8 can also be used totransfer energy back to the water in the hot water tank 10, via thesupply and return piping 28, 30 and recirculation pump 24. Thus, duringoff-peak periods (e.g., night time) the hot water system is used totransfer heat to the thermal energy storage material 8, allowing thestorage of large quantities of heat during an otherwise light energyloading period. Thereafter, during peak loading periods (e.g., daytime),the heat can be transferred back to the hot water tank or to thefurnace, as needed to heat the building air and/or water.

In addition to the condenser coil 20 arrangement, the furnace system 4may comprises a traditional fuel supply 42, and a furnace aircirculation fan 44 for drawing cold air 46 from the living space 48. Thefan 44 causes the cold air 46 to flow over the condensing coil 20, andthen circulates the heated air 50 throughout the living space 48. In oneembodiment, where the living space thermostat is set to about 70 degreesF., the cold air 46 is at a temperature of about 65 degrees F., and thehot air 50 is at a temperature of about 75 degrees F.

One appropriate thermal energy storage material is that described inU.S. Pat. No. 3,976,584 to Leifer, the entire contents of which isincorporated by reference herein. The Leifer patent describes aclathrate material that is stable at atmospheric temperature andpressure, has a melting point higher than 32 degrees F., and has arelatively high specific heat and heat of fusion. Such a materialabsorbs heat until its temperature rises to its melting point. Becauseof its high heat of fusion, the thermal storage material can absorb alarge quantity of heat per unit mass, making it a highly efficient meansof energy storage. This is but one possible material that may be used asthe thermal energy storage material 8, and other materials haveproperties that are expected to make them desirable for use as thethermal energy storage material 8. For example, materials such asimidazole, imidazolium chloride, derivatives of pyrrole, such as2-acetyl pyrrole or tetra methyl pyrrole, or other like compounds may besuitable for use as thermal energy storage material 8. The results oftesting of certain of these thermal energy storage materials arediscussed in relation to FIGS. 8-10C. Materials other than thosespecifically tested and/or identified may be suitable as well, as willbe appreciated by one of ordinary skill in the art.

The tank 6 employed to hold the thermal energy storage material willpreferably be made of a material that is non-reacting when exposed tothe particular thermal energy storage material 8 used in the ATESS.Thus, in one embodiment the tank 6 may be made from polyethylenematerial. Alternatively, the tank 6 may be made from glass ornon-reacting material or may be provided with a glass or othernon-reacting material lining.

Like the tank interior, the external surfaces of lines 22, 32 that runwithin the tank should also be non-reactive when exposed to theparticular thermal energy storage material 8 contained in the tank 6.For embodiments in which lines 22, 32 comprise copper piping or tubing,the external surfaces may be coated with an acrylic paint and wrappedwith a polymer wrap to prevent reaction between the thermal energystorage material 8 and the copper material. As an alternative to thepolymer wrap, a paraffin material may be used as a coating over theacrylic coat. Paraffin is expected to work well where the operatingtemperature of the thermal energy storage material 8 is less than about140 degrees F., since the melting point of paraffin is about 162-177degrees F. As a further alternative, lines 22, 32 could be made from apolymer material, such as polyethylene tubing (e.g., PEX tubing).Additionally, polymer coated metal tubing may be used.

The tank 6 and its connections should be sealed from the atmosphere toprevent the evaporation of water from the thermal energy storagematerial 8 during operation. Large-scale evaporation may causeundesirable changes in the thermal properties. Alternatively,evaporation may be compensated for by providing a level measurementscheme for the tank 6 so that additional water can be added to thethermal energy storage material 8 when a minimum acceptable tank levelis detected. Examples of suitable level measurement schemes may comprisea visual line-type indicator, as well as automated level detectionsystems. Additionally, in response to a low-level indication,supplemental water may be added manually by the user, or via anautomated load leveling system.

Lines 22, 32 should be arranged within the tank 6 to serve the entireheight of the tank (i.e., they should run almost to the bottom of thetank 6) to avoid solid spots within the material during operation. Thelines 22, 32 can have a U-shaped configuration, or they may be coiled.

In one embodiment, the surplus 220 Volt [V] off-peak electrical energy,which is only available for about five hours in the evening, providesthe thermal energy for heating the home and hot water needs over a 24hour day by maintaining all of the water in the hot water tank 10 atabout 120 degrees F. The 120 F hot water is circulated into a tubeheating coil 32 installed in the tank 6 used for storing the thermalenergy storage material 8, thus transferring heat energy to the material8 (solid to liquid) at a constant 77 degrees F. melting point forstorage. When the dwelling thermostat demands more heat, the ATESScompressor 24 and the furnace air circulation fan 44 starts. Therefrigerant control valve 26 provides a 40 degrees F. vaporizedrefrigerant to the evaporator coil 22 which absorbs heat from the 77degrees F. thermal energy storage material. The compressor 24 elevatesthe refrigerant temperature to 120 degrees F. to the condensing coil 20,which transfers the heat required at all times during a 24 hour day tothe circulating furnace air 46 for home heating. It is noted that thistemperature scenario applies where the living space temperature (i.e.,the thermostat set temperature) is 70 degrees F. Thus, where cooler orwarmer living space temperatures are desired, the system operatingtemperatures will adjust accordingly.

Referring to FIG. 2, an ATESS 55 is shown installed in a dwelling havingan oil or natural gas hot air furnace system 4 similar to that describedin relation to FIG. 1. In the FIG. 2 system, the energy from the furnacesystem 4 is supplemented with energy provided by one or more solar waterheating collector panels 56. In the illustrated embodiment, a solarpanel circulating water loop 58 is integrated into the hot water returnpiping 30 so that water from the hot water tank 10 can be circulatedthrough the solar energy collector panel 56. A solar panel supply line60 connects to the hot water return piping 30 between the check valve 36and the hot water tank 10 to draw water from the tank 10 and/or theoutput from the heating coil 32. A solar panel circulation pump 62 isdisposed in the supply line 60 to provide the motive circulation forcefor the water. The pumped water passes through the internal passages(not shown) within the solar panel 56, and is heated by the directenergy of the sun. The energy produced by a photovoltaic collectorportion 64 of the solar panel 56 is used to power pump 62. The heatedwater then passes to a return line 66 which directs the water back tothe hot water tank 10. The heated water can then be passed through thesupply and return piping 28, 30 using recirculation pump 34 so that theheat from the water is transferred to the thermal energy storagematerial 8 in the tank 6. It will be appreciated that the solar panel 56may be used to supplement the heat provided by the electrical resistanceheaters 52, 54, or on days of particularly direct sunlight, may be usedalone to heat the water in the hot water tank.

The energy provided to the thermal energy storage material 8 isthereafter available for use to heat the recirculated air 46 of thefurnace, or to heat the hot water contained in the hot water tank 10.

The remainder of the system 55, including the storage tank 6, thermalenergy storage material 8, and the connections between the storage tank6, the hot water tank 10 and the furnace system 4 may all be the same asdescribed in relation to the system 1 of FIG. 1.

In one embodiment, solar energy collected during sunny days as well assurplus off-peak electrical energy provided to the electrical resistanceheaters 52, 54 (which, again, may only be available for about five hoursin the evenings,) provides the thermal energy to heat the home and hotwater needs throughout a 24 hour day by maintaining all the water in thehot water tank 10 at about 120 degrees F. The 120 degree F. hot water iscirculated into the tube heating coil 32 installed in the thermal energystorage material tank 6, transferring heat energy to the thermal energystorage material 8 (solid to liquid) at a constant 77 degree F. meltingpoint for storage. When the dwelling thermostat demands more heat, theATESS compressor 24 and the furnace air circulation fan 44 start. Therefrigerant control valve 26 provides a 40 degree F. vaporizedrefrigerant to the evaporator coil 22 which absorbs heat from the 77degree F. thermal energy storage material 8. The compressor 24 elevatesthe refrigerant temperature to 120 degrees F. to the condensing coil 20,which transfers the heat required at any time during a 24 hour day, tothe circulating furnace air 46 for home heating.

Referring to FIG. 3, an ATESS 68 is installed in a dwelling having anoil or natural gas hot air furnace system 4 as well as a separate waterheating system (i.e., a heat pump) 72. The system of FIG. 3 hassubstantially the same piping, components, and interconnections asdescribed in relation to the system of FIG. 1, but also includes a heatpump system 72 that enables supplemental heating of the water in the hotwater tank 10 to accommodate high volume hot water needs during the dayand/or night.

Thus, the ATESS 68 of FIG. 3 comprises a furnace system 4, thermalenergy storage material tank 6, hot water tank 10, and all relatedpiping and fluid management components described in relation to FIG. 1.As with the systems described in relation to FIGS. 1 and 2, the ATESS 68heats the thermal energy storage material 8 during off-peak hours bycirculating hot water from the hot water tank 10 through the heatingcoil 32 in the storage tank 6.

The ATESS 68 further comprises an additional closed heating loop 72having fluid supply 74 and return 76 piping in communication withrespective evaporator and condenser coils 78, 80 located within thethermal energy storage material tank 6 and the hot water tank 10. Acompressor 82 is located in the supply line 74 and provides the motiveforce for moving the heat transfer fluid (contained within the piping74, 76) between the heat transfer coils 78, 80 in the respective tanks6, 10, thereby transferring heat from the thermal energy storagematerial 8 to the hot water located in the hot water tank 10. A controlvalve 84 is located within the return piping 76 to control the flow rateof the heat transfer fluid, thus controlling the amount of heattransferred between the thermal energy storage material 8 and the waterin the hot water tank 10.

As with the previously described embodiments, the surplus 220 V off-peakelectrical energy, which is only available for about 5 hours during theevening, provides the thermal energy to heat the home and hot water overa 24 hour day by maintaining all the water in the hot water tank 10 atabout 120 degrees F. The 120 degree F. hot water (heated by theresistance heaters 52, 54) is circulated into a heating coil 32installed in the thermal energy storage material tank 6, thustransferring heat energy to the thermal energy storage material(changing it from solid to liquid) at a constant 77 degrees F. meltingpoint for storage. When the dwelling thermostat demands more heat, theATESS compressor 24 and the furnace air circulation fan 44 starts. Therefrigerant control valve 26 provides a 40 degrees F. vaporizedrefrigerant to the evaporator coil 22 which absorbs heat from the 77degree F. thermal energy storage material 8. The compressor 24 elevatesthe refrigerant temperature to 120 degrees F. to the condensing coil 20,which transfers the heat required at all times of a 24 hour day, to thecirculating furnace air for home heating. The heat pump system 72 isoperable to heat water in the hot water tank 10 at any time of the day,using the stored heat in the thermal energy storage material 8.

Referring to FIG. 4, ATESS system 86 is installed in a dwelling havingan oil or natural gas hot air furnace system 4, and which has a separatewater heating system (i.e., a heat pump) 78 similar to that described inrelation to the ATESS of FIG. 3. In the embodiment of FIG. 4, however,the ATESS 86 is configured with a control system 87 that may reverse thefunctions of the components to enable the ATESS 86 to heat or cool thehouse as desired. Thus, on hot, humid summer days, the ATESS 86 removesheat from the house circulating air 88, and stores that heat in thethermal energy storage material 8 for heating water for home use or homeheating. The cooled air 90 is then recirculated through the dwelling.

The ATESS 86 of FIG. 4 comprises a furnace system 4, thermal energystorage material tank 6, hot water tank 10, as well as all relatedpiping and fluid management components described in relation to FIG. 3.As noted, the ATESS 86 further comprises a control system 87 operable toreverse the flow of heat transfer fluid between the storage tank 6 andthe coil 20 of the furnace system 4. This flow reversal may beimplemented by providing an appropriate piping arrangement forredirecting the flow of the heat transfer fluid according to a desiredseries of valve settings. Thus, in a “heating” setting, the flow of heattransfer fluid would be through lines 16 and 18 in the direction ofarrows “A,” and would be functional for heating the dwelling air 88. Inthe “cooling” setting, the flow of heat transfer fluid would be throughlines 16 and 18 in the direction of arrows “B,” and would be functionalfor cooling the dwelling air 88. Suitable electronics may be provided toautomatically actuate and control the direction and flow rate of theheat transfer fluid through lines 16 and 18.

Where the system 86 is used for cooling the dwelling air 88,particularly during the hot summer months in southern portions of thenorthern hemisphere, an outdoor evaporator coil and fan may be providedin communication with the heat transfer storage material 8. Thisarrangement may be of advantage where the thermal energy storagematerial 8 has met its maximum capacity for storage of rejected airconditioning heat, since it providing a path for rejecting excess heatto the outdoors.

In an alternative embodiment, in lieu of a special piping arrangementfor redirecting flow, compressor 24 could be a reversible compressor,and control valve 26 could be of a design that provides a desired degreeof flow control regardless of the direction of flow past the seat.Additionally, in lieu of control valve 26 a pair of control valves couldbe provided, one for controlling refrigerant flow rate when heat isneeded in winter or on cool summer evenings, and a second to controlrefrigerant flow if heat needs to be removed from the dwelling in thesummer. Suitable known control electronics may be provided to enableautomatic selection of a flow direction.

As with the previously-described embodiments, the ATESS 86 of FIG. 4operates to store energy in the thermal energy storage material 8 duringperiods in which such storage is most efficient. In one embodiment,energy removed from the hot air 88 of the living space is transferred tothe storage material 8 via the compressor 24, control valve 26 andpiping 16, 18 arrangement previously described. The stored energy maythen be used to heat water (in a maimer previously described)immediately or at a later time, or to heat the air circulated throughthe furnace system 4 at a later time, as needed.

Referring to FIG. 5, ATESS system 92 has substantially the same pipingand components as the system 68 described in relation to FIG. 3, andfurther comprises one or more photovoltaic solar collection panels 94 toprovide additional water and air heating for cold weather operation,such as in winter. The one or more solar collection panels 94, employingknown photovoltaic principles, may produce direct current (DC)electricity, which may then converted to alternating current (AC)electricity by a suitable AC/DC converter 96. The resulting ACelectricity may then be connected to the appropriate home or buildingpower supply circuits. A step-up or step down converter (not shown) mayalso be required to match the home or building power supply circuit. Theelectricity from the solar panels 94 may be provided directly to theresistance heaters 52, 54 that provide thermal energy to the watercontained in the hot water tank 10. This energy may then be transferredto the thermal energy storage material via lines 28, 30 and heating coil32, in a manner previously described in relation to the systems of FIGS.1-4.

The system of FIG. 5 is particularly well suited to use in cold weatherregions. Thus, when the cold weather season arrives, the availabledaytime solar power generated by the solar collection panels 94 may beused to heat water in the hot water tank for house use, and also tostore the (now converted) electrical energy in the thermal energystorage material 8 using ATESS 92. The ATESS 92, in a manner similar oridentical to that described in relation to FIG. 3, may then be used toheat the home and to meet hot water needs during any portion of a 24hour day. The off-peak surplus electric power would be back-up energyduring cloudy or limited sunny days for the net thermal energy needed toheat the residential dwelling or commercial building and/or water.

Referring to FIG. 6, ATESS system 98 has substantially the same pipingand components as the ATESS 86 described in relation to FIG. 4, andfurther comprises one or more photovoltaic solar collection panels 100for hot summer weather operation. The one or more solar collectingpanels 100 using known photovoltaic principals, may generate directcurrent (DC) electricity, which may then be converted to alternatingcurrent (AC) using a voltage converter 102, thus enabling connectionwith the home or building electric power supply. When the hot, humid,weather season arrives, the electric power generated by the solarcollection panels 100 may be used to operate the conventional airconditioning system, which operates in conjunction with the reversibleATESS 86 system described in relation to FIG. 4 to cool the air 88 inthe living space.

A storage tank 6 for use in a typical dwelling may be approximately 400gallons in volume, and may contain an energy storage material such asthat described in U.S. Pat. No. 3,976,584 to Leifer. Other appropriatethermal energy storage materials may be tetra iso-amyl ammoniumfluoride. 38 H₂0, tetra n-butyl ammonium fluoride. 18 H₂0 (ClathrateMaterials). Additionally, the following Non-Clathrate Materials may alsobe used: imidazole, imidazolium chloride, derivatives of pyrrole, suchas 2-acetyl pyrrole or tetra methyl pyrrole, or other like compounds.The heating coils 22, 32, 78 may be made of corrosion resistantmaterials suitable for carrying approximately 120 degree F. water inoperation. The total heat stored in the approximate 400 gallons ofthermal heat storage material would heat a home of approximately 1600square feet of living space maintaining a temperature of approximately70 degrees F. in the most northern latitudes of the United States dailythroughout the year. The heat stored in the approximate 400 gallon tank6 of thermal energy storage material 8 for heating the home would alsoheat water in an approximate 60 gallon insulated hot water tank 10 to adesired 115 degrees F. to 120 degrees F. temperature for normal familyhot water usage.

The ATESS may be provided with an appropriate computer control systemfor controlling the heat pump system 72, furnace system 4, recirculationpumps 34, 62 compressor 24, control valve 26, and resistance heaters 52,54 to enable the ATESS to perform as desired to compliment the oil ornatural gas heating system and/or water heating system needs of acommercial or residential building. The control system would alsocontrol the dwelling heat transfer (i.e., heat pump) system as a dualsystem to remove heat from the air circulating in the furnace ductsystem during the hot and humid summer days, and to that heat in thethermal energy storage material stored in the storage tank 6. The systemmay be used in conjunction with a conventional electric powered airconditioning system during the hot-humid summer months.

It will also be appreciated that the ATESS may be integrated into amobile platform to aid in the transport of perishable commodities suchas orange juice and the like. Thus, the ATESS may be sized andconfigured for installation in railroad cars, trucks, planes,container/cargo ships or other transportation platforms. In one example,the ATESS may be combined with solar panels or fuel oil to reduce oilconsumption in ocean going passenger ships.

Further, the ATESS may be used as part of a system for reducing theenergy consumption required for any of a variety of industrial processesthat require substantial energy, such as soup making, and the like.

In yet another embodiment, the ATESS may be used to advantage inapplications such as commercial/personal ice skating or hockey rinks.

Advantages

The Northeast area of the United States has the larger number of homesand commercial buildings heated by oil and liquefied natural gas (LPG).Due to the lack of major natural gas pipelines serving the area,liquefied natural gas is imported through major seaports in theNortheast by huge tankers from foreign countries, which could be aterrorist threat to the security of our seaports. The conversion toATESS of homes and commercial buildings to electric off peak power orsolar energy would eliminate these shipments and the associated threatsto our seaports.

The United States currently imports approximately 40% of its domesticoil needs from foreign countries. The ATESS system can substantiallyreduce or eliminate the need for foreign oil.

ATESS can also reduce the need to heat residential dwellings orcommercial buildings with oil and natural gas. ATESS can reduce daytimepeak electric power demands during hot and humid weather.

ATESS can store solar thermal energy available during the daytime foruse during day or night for energy needs of residential dwellings orcommercial buildings. ATESS, if widely used in residential dwellings andcommercial buildings, will allow electric power generation networks topractice load leveling between peak daytime and surplus off-peak nighttime electric power demands.

Laboratory Test Results for Various Thermal Energy Storage Materials

The inventors have conducted laboratory tests to determine the meltingpoint, heat of fusion and safe operating temperature range of severalmaterials considered suitable for use as thermal energy storage material8. The results of the inventors' tests are shown in Table 1 below. Inaddition to the specific clathrate material the inventors used in theirtests, other potentially useful clathrate materials exist and are notedherein. These materials include: tetra iso-amyl ammonium fluoride 38H₂O, which has a melting point of 88 degrees F., and tetra n-butylammonium fluoride 18 H₂O, which has a melting point of 98.6 degrees F.It should be noted that some of the other thermal energy storagematerials identified in Table 1 below have melting points much greaterthan 77 degrees F. The use of these higher melting point materials inany one of the previously described ATESS systems may preclude the needfor a heat pump system 72.

TABLE 1 Physico-Chemical Results of Potential Tested Thermal EnergyStorage Materials Melting Heat of % Heat of Safe Operating Point FusionFusion of Range Materials (degrees F.) (BTU/lbs) Water (%) (degrees F.)TESM 1¹ 77 108 75%  77-140 Imidazole 194 75 52% 194-320 Imidazolium 32060 42% 320-375 Chloride 2-Acetylpyrrole 195 77 54% 195-260 ¹“TESM 1” was(n-C₄H₉) 4NF 32.8 H₂O

Note that the “Safe Operating Range” indicated in Table 1 represents,for each TESM, a temperature range between the melting point of the TESMand a point approximately 5-20 degrees F. below the decompositiontemperature of the particular TESM.

Test Site Results

Referring to FIG. 7, a test site building was constructed as ahorizontal duplex, with each room (Rooms #1 and #2) being approximately32 square feet. Room #1 was heated conventionally, while Room #2 washeated using the ATESS. The inventors used 40 lbs of Thermal EnergyStorage Material (TESM) 8, which in this case was (n-C₄H₉) 4NF 32.8 H₂O,and which will be referred to hereinafter as “TESM 1.” The TESM 1 wascontained in TESM 1 tank 6. For the purposes of the test, the tank 6 wasa 5 gallon polyethylene tank. Internal piping was copper, coated withacrylic coating and wrapped with a polymer film. The tank 6 connectionswere sealed from the atmosphere using tape to prevent evaporation. The40 lbs. of TESM 1 stored heat energy from two (2) limited sources inthese tests. Source 1 was evening off peak electricity and Source 2 wasdaytime solar energy. The solar heat collection system worked well, butdue to the lack of sunny days during the test, the inventors simulatedthe daytime solar heat by using metered daytime electric power. Bothsources were limited to four (4) hours per cycle for the tests. TheATESS in Room #2 was a scaled down version of the ATESS previouslydescribed in relation to FIG. 2.

FIG. 8 shows the results of 14 days of testing. Days 1, 2, and 3 wereconducted to determine the heat required to maintain a consistenttemperature in Rooms #1 and #2. The results of these tests show the heatrequired to maintain the same temperature in Rooms #1 and #2 areessentially the same.

FIG. 8 also shows test days #4 through #14 which were conducted usingonly the ATESS heating system as a primary heat source for Room #2. Testdays #4 and #5 were not considered in the results because those daysused 3.0 and 3.5 hour heating cycles to transfer heat to the TESM, andthese shorter cycle times were deemed not to be long enough for transferof an adequate amount of heat to TESM 1 for storage during the tests.The remaining test days (#6 to #14) used four (4) hour TESM heatingcycles. The results show that ATESS heating system works very well tomaintain the temperature in Room #2 at a nominal 70 degrees F.(temperature actually ranged from about 68-71 degrees F.) without theuse of any conventional additional heat from fuel oil or gas. During theDecember and January tests, the outside air temperature fluctuated froma low of 12 degrees F. to a high of 47 degrees F.

FIG. 9 shows the performance of the ATESS heating system hour by hourduring a 24-hour day. The results in FIG. 9 were compiled for an optimumday (i.e., one close to the mean of test days 6-14) using the ATESS. Theresults show energy from two (2), limited sources (i.e., evening offpeak electricity and daytime solar) being distributed as needed to testRoom #2 in order to maintain a desired temperature. Some heat from theATESS control system, compressor motor losses, and heat of compressionfrom the compressor were also added to Room #2. The limited sourceenergy from non-peak electric and solar was stored in the TESM 1 duringthe limited 4 hour cycles and then distributed to Room 2 by the ATESSheat pump system. The heat needed to maintain 70 degrees F. in Room 2was controlled by the thermostat of the ATESS system.

The results tabulated in FIGS. 8 and 9 show heat pump inefficiencies ofour system design which can be substantially improved by an experiencedheating and ventilation equipment manufacturer. For example, the ATESSsystem prototype heat pump evaporator coil comprised single diametercopper tubing. An experienced HVAC engineer could design an evaporatorcoil having a varied diameter in order to maintain a constant evaporatorrefrigerant temperature of approximately 40 degrees F. across the entirecoil. Additionally, the prototype heat pump system had less than optimalelectric compressor motor efficiency, which may be improved greatly inlarge system designs using either AC or DC electric power. Additionally,modern control systems applied to a large-scale ATESS would use littleelectric power as compared to the prototype system. The ATESS heatingsystem inefficiency is indicated in FIGS. 8 and 9 as extra heat added toroom #2 (“Motor Loss and Extra Room Heat Demand”) to maintain thedesired temperature.

The inventors consider that to install an operational ATESS into a fullsize residential home having 1600 sq ft. of living area would require a50:1 scale up to replicate the results shown at the test site. FIGS.10A-C show the daily fuel oil and LPG (liquid propane gas) consumptionfor such a residential home. In addition, FIGS. 10A-C shows a comparisonof the annual winter heating costs for: a) fuel oil, b) LPG, and c) theATESS heating system using: 1) off peak electric and daytime solar, 2)all off peak electricity, and 3) all daytime solar.

The results indicate a substantial cost savings can be achieved throughuse of the ATESS. For example, the annual cost for fuel oil using a 125day annual winter heating cycle is estimated to be about $1,813, whilethe annual cost for LPG also using a 125 day annual winter heating cycleis estimated to be $1,932. (These estimated costs where calculated usingestimates of $2.55/gallon of fuel oil and $1.86/gallon of LPG.) Bycomparison, the annual heating cost using the ATESS for the 125 dayannual winter heating cycle with: 1) off peak electric and daytime solaris estimated to be about $1,048; 2) all off peak electric is estimatedto be about $1,348; and 3) all daytime solar is estimated to be about$748. Thus, it can be seen that there would be a considerable savingswith the use of the ATESS as compared to conventional heating methods.This savings can be increased by adding accessories to heat water.

For example, during hot summer months, heat may be removed from thedwelling space (via air conditioning) and stored in the TESM.Appropriate piping and pumping equipment (e.g., items 72, 83 in FIG. 4)may be added to the ATESS to allow transfer of this stored heat from theTESM 8 to the hot water in the hot water tank 10 to maintain a desiredtemperature (e.g., 130 degrees F.). Heating the hot water in this mannermay eliminate or reduce the need to use expensive daytime electric, fueloil or LPG.

FIGS. 10A-C further show the gallons per day of fuel oil and LPG as wellas the total annual costs for a 125 day winter heating season.

In addition to the aforementioned cost savings, the use of the ATESS mayalso result in substantial reductions in pollutants emitted to theatmosphere as compared to conventional heating systems. For example, theburning of fuel oil (for the annual heating season) emits to theatmosphere 3,831 lbs of carbon and 14,060 lbs of CO₂ per residence(again assuming a 1600 square foot living space). The burning of LPGemits 2,927 lbs of carbon and 10,742 lbs of CO₂, for the same sizeliving space. The ATESS, by contrast, emits no carbon or CO₂ to theatmosphere. These results are clearly shown at the bottom of FIG. 10C.

SUMMARY

The inventors have shown that using the disclosed ATESS heating systemas a compliment or a primary heating system:

(1) Substantially reduces the need for fuel oil and/or liquid petroleumgas (LPG) for heating homes or industrial buildings.

(2) Substantially reduces both carbon and carbon dioxide (CO₂) emissionswhich contributes to global warming.

(3) Substantially reduces the need to transport surplus generated offpeak electrical power from local grids, because it can be stored in theTESM for use at anytime during a 24-hour day.

(4) ATESS heating systems allow for the use of solar energy obtainedduring daylight hours because it can be stored in the TESM for useanytime during a 24-hour day. ATESS will also reduce the number of solarpanels required to be installed to provide needed energy for a dwellingor industrial building.

(5) ATESS heating systems, as proven in the inventors' prototype tests,would considerably reduce the country's dependence on foreign oil andLPG, thereby improving homeland security.

Although the invention has been described in terms of exemplaryembodiments it will be apparent to those skilled in the art that variouschanges and modifications can be made thereto without departing from thespirit and scope of the invention.

1. A method for operating an energy storage system, comprising:providing a first volume of heat transfer fluid; providing a secondvolume of thermal energy storage material (TESM), the TESM comprising asubstantially solid material having a melting point above 32 degreesFahrenheit (F), and a latent heat of fusion approaching that of water;and providing a heating coil in contact with the second volume;circulating the heat transfer fluid through the heating coil in thesecond tank; wherein the step of circulating the heat transfer fluidtransfers heat from the heat transfer fluid to the TESM when thetemperature of the TESM is less than the temperature of the heattransfer fluid; and wherein the step of circulating the heat transferfluid transfers heat from the TESM to the heat transfer fluid when thetemperature of the TESM exceeds the temperature of the heat transferfluid.
 2. The method of claim 1, further comprising the step of heatingthe heat transfer fluid using a heater.
 3. The method of claim 1,further comprising: providing a solar panel having a fluid-filledrecirculation loop in fluid communication with the heating coil of thesecond tank; and moving the heating fluid through the recirculation loopand through the heating coil to transfer heat from the heating fluid tothe TESM.
 4. The method of claim 1, further comprising: providing an airconditioning loop for moving an air conditioning fluid between a firstair conditioning coil disposed in said second tank and a second airconditioning coil disposed in a ventilation supply opening; and movingthe air conditioning fluid within the air conditioning loop to transferenergy between the TESM and air directed over an outer surface of saidsecond air conditioning coil.
 5. The method of claim 4, furthercomprising controlling a flow rate of said air conditioning fluidthrough said air conditioning loop using at least one of a compressorand a control valve.
 6. The method of claim 5, further comprisingoperating the compressor in a first operating mode to move the airconditioning fluid through the air conditioning loop in a firstdirection, and operating the compressor in a second operating mode tomove the air conditioning fluid through the air conditioning loop in asecond direction opposite to said first direction.
 7. The method ofclaim 1, wherein the TESM comprises a material selected from the groupconsisting of clathrate, imidazole, imidazolium chloride and aderivative of pyrrole.
 8. A method for operating an energy storagesystem, comprising: providing a first tank for holding a quantity offluid; providing a second tank having a quantity of thermal energystorage material (TESM) disposed therein, the TESM comprising asubstantially solid clathrate having a melting point above 32 degreesFahrenheit (F); and providing a fluid connection loop between the firstand second tanks, the fluid connection loop being in fluid communicationwith the first tank and comprising a heating coil disposed within thesecond tank; moving the fluid within the fluid connection loop totransfer heat from the fluid in the first tank to the TESM in the secondtank when the fluid in the first tank has a temperature greater than atemperature of the TESM; and moving the fluid within the fluidconnection loop to transfer heat from the TESM in the second tank to thefluid in the first tank when the TESM has a temperature greater than thetemperature of the fluid in the first tank.
 9. The method of claim 8,further comprising heating the fluid in the first tank using a heater.10. The method of claim 8, further comprising: providing a solar panelhaving a fluid-filled recirculation loop engaged with the fluidconnection loop; and moving the fluid within the recirculation loop andthe fluid connection loop to transfer heat from the solar panel to theTESM.
 11. The method of claim 8, further comprising: providing an airconditioning loop comprising a first air conditioning coil disposedwithin said second tank and a second air conditioning coil disposedwithin a building ventilation supply opening; and moving an airconditioning fluid within said air conditioning loop to transfer energybetween the TESM and air directed over an outer surface of the secondair conditioning coil.
 12. The method of claim 11, further comprisingoperating at least one of a compressor and a control valve to control aflow rate of said air conditioning fluid through said air conditioningloop.
 13. The method of claim 12, further comprising operating thecompressor in a first operating mode to move said air conditioning fluidthrough said air conditioning loop in a first direction, and operatingthe compressor in a second operating mode to move the air conditioningfluid through said air conditioning loop in a second direction oppositeto said first direction.
 14. The method of claim 8, wherein the TESMcomprises a material selected from the group consisting of clathrate,imidazole, imidazolium chloride and a derivative of pyrrole.
 15. Amethod for operating a thermal energy storage system, comprising:providing a first tank, a second tank, and an air distribution system;the first tank having a quantity of water disposed therein; and thesecond tank having a quantity of Thermal Energy Storage Material (TESM)disposed therein, the TESM comprising a phase change material having amelting point above 32 degrees Fahrenheit (F), and a latent heat offusion approaching that of water; moving water between the first andsecond tanks via a recirculation loop, the recirculation loop comprisingat least a first coil disposed in the second tank; moving a first heattransfer fluid between the second tank and the air distribution systemvia an air conditioning loop comprising a first air conditioning coildisposed in the second tank and a second air conditioning coil disposedin the air conditioning system to transfer energy between the TESM andair passed over the second air conditioning coil.
 16. The method ofclaim 15, further comprising: providing a heat pump loop comprising asecond heat transfer coil disposed within the first tank, and a thirdheat transfer coil disposed within the second tank; and moving a secondheat transfer fluid within the heat pump loop to transfer energy betweenthe TESM in the second tank and the water in the first tank.
 17. Themethod of claim 16, further comprising: operating at least one of afirst compressor and first control valve to control movement of the heattransfer fluid through said air conditioning loop, and operating atleast one of a second compressor and a second control valve to controlmovement of the second heat transfer fluid through the heat pump loop.18. The method of claim 17, wherein the first compressor is a reversiblecompressor.
 19. The method of claim 15, further comprising: providing asolar panel having a solar panel fluid loop in fluid communication withthe recirculation loop between the first and second tanks; and movingfluid within the solar panel fluid loop and through the recirculationloop to transfer energy from the solar panel to the TESM.
 20. The methodof claim 15, further comprising: providing a solar panel for generatinga current for electrical power, and heating the first tank using aheater powered by said electrical power.
 21. The method of claim 15,wherein the TESM comprises a material selected from the group consistingof clathrate, imidazole, imidazolium chloride and a derivative ofpyrrole.
 22. The method of claim 15, wherein the TESM comprisesclathrate.
 23. A method of operating a thermal energy storage system,comprising: providing a first volume of heat transfer fluid; providing asecond volume of Thermal Energy Storage Material (TESM), the TESMcomprising a phase change material having a melting point above 32degrees Fahrenheit (F), and a latent heat of fusion approaching that ofwater; providing a radiator circulation system; moving the heat transferfluid through a first coil in contact with the TESM to transfer energybetween the heat transfer fluid and the TESM; and moving a second heattransfer fluid from a second coil in contact with the second volume to athird coil disposed in the radiator circulation system to transferenergy between the TESM and a fluid passed over the third coil.